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Articles 391 - 420 of 654
Full-Text Articles in Civil and Environmental Engineering
Dissolved Carbon Dioxide For Scale Removal In Reverse Osmosis, Erin Partlan
Dissolved Carbon Dioxide For Scale Removal In Reverse Osmosis, Erin Partlan
All Theses
Membrane fouling is a major operational issue in reverse osmosis (RO) desalination plants. In particular, plants treating brackish groundwater can encounter troublesome inorganic scales, including carbonates, sulfates, and silicates. A novel cleaning method is proposed to remove inorganic scales from fouled RO membranes usinag dissolved CO 2 . As CO2 molecules encounter membrane foulants, the surfaces serve as nucleation sites for small bubbles to form and shear off foulants. Dissolved CO2 solutions were prepared by bubbling CO2 gas into water held in a pressure vessel. Gas dissolution was confirmed by enhanced exit velocities for water containing CO …
Evaluating The Predictive Capability Of Numerical Models Considering Robustness To Non-Probabilistic Uncertianty In The Input Parameters, Parker Shields
Evaluating The Predictive Capability Of Numerical Models Considering Robustness To Non-Probabilistic Uncertianty In The Input Parameters, Parker Shields
All Theses
The paradigm of model evaluation is challenged by compensations between various forms of errors and uncertainties that are inherent to the model development process due to, for instance, imprecise model input parameters, scarcity of experimental data and lack of knowledge regarding an accurate mathematical representation of the system. When calibrating model input parameters based on fidelity to experiments, such compensations lead to non-unique solutions. In turn, the existence of non-unique solutions makes the selection and use of one `best' numerical model risky. Therefore, it becomes necessary to evaluate model performance based not only on the fidelity of the predictions to …
Optimization Of Porous Pavement Mixtures Based On Aggregate Structure, Andrew Neptune
Optimization Of Porous Pavement Mixtures Based On Aggregate Structure, Andrew Neptune
All Dissertations
Porous pavements are sustainable features that are used to help manage the quantity and quality of stormwater runoff. These pavements may include porous asphalt, permeable interlocking concrete pavers and pervious concrete. Since pavements that are purposefully designed to drain water through their matrix are relatively new, contractors and engineers are faced with various challenges such as improper design and installation, poor workability, and excessive finishing which may lead to clogged pores. Therefore, this study on porous pavements examined pervious concrete mixtures to evaluate an optimization process for the preparation of porous pavement mixtures based on aggregate structure to meet desired …
Assessing Potential Environmental Impacts According To Probable Patterns Of Switchgrass Adoption In The Southeastern Us, Benjamin Sharp
Assessing Potential Environmental Impacts According To Probable Patterns Of Switchgrass Adoption In The Southeastern Us, Benjamin Sharp
All Dissertations
To assess the overall net impact of an emerging technology, life cycle assessment (LCA) must be accompanied by projections of adoption. Diffusion of innovation research provides tools that incorporate economic and social variables to explain and forecast integration of technologies. A switchgrass-to-ethanol case study for the southeastern U.S. is used to demonstrate methods for gauging aggregate environmental effects of an emerging energy technology. Before applying diffusion concepts, breakeven capacities are calculated for land in row crops, hay, pasture and marginal land. Breakeven curves are generated to provide upper bounds to switchgrass adoption over a range of farm-gate prices. The amount …
Seismic Site Coefficient Model And Improved Design Response Spectra Based On Conditions In South Carolina, Shimelies Aboye
Seismic Site Coefficient Model And Improved Design Response Spectra Based On Conditions In South Carolina, Shimelies Aboye
All Dissertations
A new seismic site coefficient model is developed from the results of over 60,000 total stress, one-dimensional equivalent ground response simulations assuming conditions in South Carolina. Computed site coefficients ( F ) are plotted versus average shear wave velocity in the top 30 m (VS30 ) and grouped by location, spectral acceleration (Soutcrop ) and spectral period. Locations considered in the Coastal Plain include Aiken, Charleston, Columbia, Florence, Lake Marion, Myrtle Beach, and the South Carolina side of Savannah. Locations considered in the Piedmont include Columbia, Greenville, Greenwood, and Rock Hill. In all the plots of …
Renovation Of Ammonia Contaminated Produced Water Using Constructed Wetlands, Donald Beebe
Renovation Of Ammonia Contaminated Produced Water Using Constructed Wetlands, Donald Beebe
All Dissertations
Pilot-scale wetland treatment systems were designed and constructed to evaluate renovation of simulated oilfield produced water contaminated with ammonia (20 mg/L ammonia-N). A process-based pilot-scale constructed wetland was designed to meet specific biogeochemical conditions for conversion of ammonia to nitrogen gas through microbial nitrification and denitrification. The process-based constructed wetland treated the simulated produced water to meet stringent discharge requirements (less than 1.2 mg/L ammonia-N). Clinoptilolite, a zeolite mineral, was evaluated for use in constructed wetlands to increase ammonia sorption and nitrification activity. Clinoptilolite increased wetland ammonia sorption capacity and served as a microbial carrier for nitrifying bacteria when ranges …
Flexural Strength Reliability Of Visually Graded Southern Pine Dimensional Lumber, Mengyu Yang
Flexural Strength Reliability Of Visually Graded Southern Pine Dimensional Lumber, Mengyu Yang
All Theses
The reference design values published in the National Design Specification (NDS) for Wood Construction are derived from full-scale testing of lumber samples performed in the 1980s. This testing program is commonly known as the In-GradeTest Program. Selective annual sample tests of visually graded Southern Pine lumber from 1994 to 2010 revealed an overall decreasing trend in the mechanical properties. Because of this alarming observation, a new round of full-scale In-Grade test of visually graded Southern Pine was initiated in 2010. The new test data indicated significant reductions in certain design values published in the current design code (2005 NDS). …
Improvement Of Onsite Wastewater Treatment By Use Of Electrically Conductive Carbon Cloth, Christopher Weber
Improvement Of Onsite Wastewater Treatment By Use Of Electrically Conductive Carbon Cloth, Christopher Weber
All Theses
The purpose of this research is primarily focused on carbon oxidation in domestic septic systems. Small-scale septic waste reactors utilizing electrically conductive carbon cloth were assessed for improving carbon oxidation and therefore the overall efficiency of on-site wastewater treatment systems.
A bioelectrochemical system was developed to enhance carbon oxidation in septic systems using electrically conductive carbon cloth as an anode/cathode bridge to transfer electrons from strictly anoxic septic wastewater to an oxic system outside of the septic reactor. This 'septic snorkel' (so named since the system 'breathes' via the carbon cloth extends into an aerobic zone) was designed to lower …
Robust Design Optimization: Ensuring Robustness Against Uncertainty In Structural Design, Zhifeng Liu
Robust Design Optimization: Ensuring Robustness Against Uncertainty In Structural Design, Zhifeng Liu
All Dissertations
In structural design, if robustness is overlooked in design process, the acquired design is likely to have large variation in its performance due to uncertainties. In that there is no design specification that explicitly considers the robustness against such uncertainties, this dissertation elucidates design methodologies for use in selecting the optimal design parameters to minimize the effect of the hard to reduce or irreducible uncertainties on structural performance, i.e., maximizing the robustness. However, due to limited resources, structural designs are also constrained by available resources and budget. Consequently, in that a tradeoff relationship exists between the robustness and cost (i.e. …
Removal Of N-Nitrosodimethylamine And Trihalomethane Precursors With Powdered Activated Carbon, Wilson Beita Sandi
Removal Of N-Nitrosodimethylamine And Trihalomethane Precursors With Powdered Activated Carbon, Wilson Beita Sandi
All Theses
N-nitrosodimethylamine (NDMA) has been used commercially in several applications, including the production of liquid rocket fuel, and a variety of foods, but gained more relevance when it was discovered as a drinking water disinfection by-product (DBP) in 1989. NDMA is a probable human carcinogen with 10-6 lifetime cancer risk associated with a drinking water concentration of 0.7 ng/L, and is listed as a priority pollutant in the Code of Federal Regulations; no federal maximum contaminant level has been established for drinking water yet. However, the United States Environmental Protection Agency is planning to make a preliminary regulatory determination in 2013 …
Data Driven, Performance Based Parking Management In A University Setting, Brian Maleck
Data Driven, Performance Based Parking Management In A University Setting, Brian Maleck
All Theses
With university enrollment increasing, campuses are becoming under increased strain for parking. More students results in more cars on an already stressed parking infrastructure. In many instances, university parking management offices are being asked to accommodate this increase in parking without the construction of new parking infrastructure. In order to accommodate these demands, better parking management is required.
This research develops a framework to evaluate current parking management practices and pinpoint methods to improve upon current practices. The framework is generalized for use by any size and type of university. Clemson University's campus in Clemson, SC was used as a …
Removal Of Arsenic From Simulated Groundwater Using A Pilot-Scale Constructed Wetland Treatment System, Jeffrey Schwindaman
Removal Of Arsenic From Simulated Groundwater Using A Pilot-Scale Constructed Wetland Treatment System, Jeffrey Schwindaman
All Theses
A pilot-scale constructed wetland treatment system (CWTS) was designed and built to produce biogeochemical conditions that promoted targeted processes for removal of arsenic from simulated groundwater. Two series were designed to promote co-precipitation and sorption of arsenic with iron oxyhydroxides under oxidizing conditions, and two series were designed to promote precipitation of arsenic sulfide and co-precipitation of arsenic with iron sulfide under reducing conditions. The two major objectives were to (1) assess arsenic removal performance and (2) determine the fate and distribution of arsenic in each series. Results indicate that arsenic removal performance was greater in series designed to promote …
Probabilistic Back Analysis Of Geotechnical Systems, Lei Wang
Probabilistic Back Analysis Of Geotechnical Systems, Lei Wang
All Theses
This thesis is aimed at applying the probabilistic approaches for back analysis of geotechnical systems. First, a probabilistic back-analysis of a recent slope failure at a site on Freeway No. 3 in northern Taiwan is presented. The Markov Chain Monte Carlo (MCMC) simulation is used to back-calculate the geotechnical strength parameters and the anchor force. These inverse analysis results, which agree closely with the findings of the post-event investigations, are then used to validate the maximum likelihood method, a computationally more efficient back-analysis approach. The improved knowledge of the geotechnical strength parameters and the anchor force gained through the probabilistic …
Evaluation Of Anaerobic Biodegradation Of High Concentrations Of Halogenated Methanes, Priya Rachel Jacob
Evaluation Of Anaerobic Biodegradation Of High Concentrations Of Halogenated Methanes, Priya Rachel Jacob
All Theses
Removal of the chlorinated methanes, carbon tetrachloride (CT), chloroform (CF) and dichloromethane (DCM), and the halogenated methane, trichlorofluoromethane (commonly known as CFC-11 or Freon-11) from contaminated soil and groundwater remains challenging. Releases to the environment resulted from historically poor disposal practices, as well as spills and leaks from underground storage tanks. Among these three compounds, CF is considered the benchmark for evaluating the feasibility of bioremediation, due to its typically high level of toxicity towards most anaerobic prokaryotes. However, inhibitory effects of low concentrations of CFC-11 on anaerobes have been reported as well. Bioremediation is an attractive option for clean-up, …
Describing Plutonium Contamination Issues In Hanford Soils: Development Of A Thermodynamic Surface Complexation Model, Sarah Herr
All Theses
The development of remediation strategies for long-term site management requires knowledge of an actinide's geochemical behavior. Understanding this behavior can lead to the formation of a subsurface transport model. For example, plutonium mobility in the subsurface environment is significantly influenced by oxidation-reduction and complexation reactions. This work considered the surface-mediated reduction of plutonium, as well as the hydrolysis and carbonate complexation of the actinide.
Evaluating the significance of these reactions required several variable pH batch sorption studies. Experiments incorporated plutonium and neptunium sorption to sediments from the Hanford Nuclear Reservation in Washington State. Two different sediments were examined: coarse-grained and …
Corrosion Activity In Precast Concrete Elements And Cementitious Closure Pours, Shabi Abbas Udaipurwala
Corrosion Activity In Precast Concrete Elements And Cementitious Closure Pours, Shabi Abbas Udaipurwala
All Theses
The use of prefabricated elements in the construction of highway bridges has been a common practice in the United States since 1950s. Precast concrete adjacent box beam girder bridges are quite popular given that the precast elements not only have structural capacity to span across the supports, but also form the bridge deck. These bridges have generally performed well during the initial years after construction, but recent failures in Pennsylvania and Indiana have aroused a nationwide alarm to investigate the causes of failure and find solutions to repair these bridges or develop design for new replacement bridges. It was found …
Development Of A Rating System To Measure The Vulnerability Of Residential Homes To Natural Hazards, Corey Cattano
Development Of A Rating System To Measure The Vulnerability Of Residential Homes To Natural Hazards, Corey Cattano
All Dissertations
Hurricanes and tropical storms continue to damage the United States coastline where population migration increases and tourism thrives. Extended dry spells, high winds, and hot summers in the Mountain and Pacific West regions promote ideal conditions for seemingly uncontrollable wildfires. Additionally, the increased frequency of unstable climate conditions foretells signs of Mother Nature not letting up. With recent events such as Superstorm Sandy and the Waldo Canyon wildfires in mind, there is a strong need to improve hazard mitigation techniques in residential homes and encourage resilient building methods. Research within this field is challenging due to the lack of descriptive …
Miniature Concrete Prism Test - A New Test Method For Evaluating The Asr Potential Of Aggregates, The Effectiveness Of Asr Mitigation And The Job Mixture, Enamur Latifee
All Dissertations
Existing test methods to characterize ASR potential of aggregates and mitigation ability of supplementary cementing materials such as the Accelerated Mortar Bar Test (AMBT) and the Concrete Prism Test (CPT) are widely accepted in the industry. Although, the AMBT is a rapid test, the results from this test can be unreliable, particularly with certain types of aggregates. The CPT is considered as a more reliable test; however, the duration of this test method renders it impractical for routine usage in the industry to screen deleterious materials or inefficient ASR mitigation measures. This research presents a new test method-Miniature Concrete Prism …
Effect Of Differential Movement Of Straight Reinforcing Bars During Early Age Curing On The Bond Strength, Tyler Andrews
Effect Of Differential Movement Of Straight Reinforcing Bars During Early Age Curing On The Bond Strength, Tyler Andrews
All Theses
As the nation's infrastructure continues to age, the number of structural deficiencies is rising. Accordingly, there is a great need and desire to replace these failing components in a quick and efficient fashion. Prefabricated elements for structures such as bridges and parking decks are commonly implemented in this process in order to save both time and money. These prefabricated elements are often subjected to moving live loads during construction and repair which, consequently, result in differential movements occurring across the joints connecting the elements of these structures. Potential reductions in joint capacity, joint stiffness, and structural durability are the byproducts …
Air Pressure Energy Storage For Reverse Osmosis: Bench-Scale Proof Of Concept, Ying Sun
Air Pressure Energy Storage For Reverse Osmosis: Bench-Scale Proof Of Concept, Ying Sun
All Theses
Society faces diminishing access to clean drinking water because of increasing global population and the development of modern industries. At the same time, climate change and other environmental problems caused by the increase in fossil fuel consumption the emphasis on reducing dependency on traditional energy resources in the process of potable water production. To address both problems, a small-scale wind powered reverse osmosis (RO) desalination system with a unique energy storage mechanism was envisioned to provide an energy buffer such that fluctuating and intermittent wind can be utilized. Energy is stored in the form of compressed air in a pressure …
An Analysis Of A Missing Design Concept For Sustainable Buildings: Addressing The Safety And Health Of The Construction Worker, Christopher Almond
An Analysis Of A Missing Design Concept For Sustainable Buildings: Addressing The Safety And Health Of The Construction Worker, Christopher Almond
All Theses
Construction work is inherently dangerous. The 2010 U.S. Bureau of Labor Statistics show the construction industry had the most fatal injuries of all industry sectors, 17%. U.S. regulations place the responsibility for construction safety on the construction contractor. However, owners and designers have the potential to affect the safety of the construction workforce. Owners have gotten more involved in promoting the safety and health of construction workers in recent years; however, studies show that the safety and health of the construction workforce is not typically considered by designers.
The Naval Facilities Engineering Command (NAVFAC) - the U.S. Navy's systems command …
The Extraction Of Acetic Acid From Thermotoga Neapolitana Fermentation Spent Medium Using Fresh/Recovered Aliquat 336 And Produce Cma, Yifan Du
All Theses
To offer an alternative pathway to produce calcium magnesium acetate (CMA) as an environmental friendly deicer to relieve the pressure on fossil fuels demand, a liquid-liquid extraction process was studied. This process includes using Aliquat 336 (tri-n-octylmethylammonium chloride) diluted in kerosene as an organic extractant to extract acetic acid from Thermotoga neapolitana fermentation spent medium, which contained 34 g/L of acetic acid and 10 g/L of NaCl.
The extraction efficiency of Aliquat 336 was studied under several different extraction conditions. The initial pH of the spent medium was adjusted to a pH range of 2.25 to 5.75 with a 0.5 …
Impact Of Channel Conditions On Existing Scour Measuring Instruments, Md Nasimul Hoque Chowdhury
Impact Of Channel Conditions On Existing Scour Measuring Instruments, Md Nasimul Hoque Chowdhury
All Theses
Scour around bridge piers and abutments, is the prominent reason for bridge failures. Bridge failures have substantial effects on economy and human lives. About 60% of the total bridge failures in U.S. can be attributed to scour. In the past, scour has been responsible for several million dollars in bridge repair cost. Given the threat to the bridge infrastructure due to scour, the U.S. Federal Highway Administration has proposed several countermeasures to reduce the impact of bed degradation. One of these countermeasures that is particularly relevant during peak flow periods is the real-time scour monitoring. Scour monitoring involves real-time data …
Application Of Parameter Estimation And Calibration Method For Car-Following Models, Md Rahman
Application Of Parameter Estimation And Calibration Method For Car-Following Models, Md Rahman
All Theses
Both safety and the capacity of the roadway system are highly dependent on the car-following characteristics of drivers. Car-following theory describes the driver behavior of vehicles following other vehicles in a traffic stream. In the last few decades, many car-following models have been developed; however, studies are still needed to improve their accuracy and reliability.
Car-following models are a vital component of traffic simulation tools that attempt to mimic driver behavior in the real world. Microscopic traffic simulators, particularly car-following models, have been extensively used in current traffic engineering studies and safety research. These models are a vital component of …
Modeling Benefits Of Implementing Low Impact Development Practices Within Forecasted Growth Scenarios Of The Reedy River Watershed, Stephen Taylor
Modeling Benefits Of Implementing Low Impact Development Practices Within Forecasted Growth Scenarios Of The Reedy River Watershed, Stephen Taylor
All Theses
For this research, a previously developed comprehensive watershed water quality model for the Reedy River as developed for South Carolina Department of Health and Environmental Control (SCDHEC) and the US Environmental Protection Agency (EPA) as a total maximum daily load (TMDL) assessment tool was used to assess the benefits of using low impact development (LID) designs in future growth of Greenville County, within the Reedy River watershed. The original intent of this model was to provide SCDHEC with a defensible model that could be used to prepare nutrient TMDLs for an area located at Boyd Millpond and the Reedy River …
Hydraulic Impact Of Porosity Distribution And Hydrologic Characterization Of Porous Pavements, William Martin
Hydraulic Impact Of Porosity Distribution And Hydrologic Characterization Of Porous Pavements, William Martin
All Dissertations
This research focused on the hydrologic characterization of porous pavement and pavement properties that can affect its hydraulic behavior. The first of these properties investigated was the presence of a vertical porosity distribution which can significantly impact the infiltration rate. A method utilizing image analysis was tested and experimentally verified. The representative elemental area (REA) was needed for this imaging method and was found to be 83.9 cm2 (13 in2). To convert the porosity distribution into a permeability distribution the relationship between porosity and permeability was found using homogenous samples. From the resulting permeability distribution an effective permeability was found …
Development Of An Environmental And Operational Impact Assessment Framework For Connected Vehicle Technology Supported Alternative Fuel Vehicles, Parth Bhavsar
All Dissertations
The efforts of US automobile manufacturers to introduce Alternative Fuel Vehicles (AFVs) to the automobile market, and reduce fossil fuel dependency are changing the energy consumption scenario of the US transportation network. The evolution in Connected Vehicle Technology (CVT) is further accelerating the vision of a safe and sustainable transportation system for the 21st century. However, before such system can be an actuality to meet future US transporation needs, a new generation of traffic micro-simulation tools must be developed to evaluate connected vehicle technologies that can support AFVs in the transportation network.
This research focused on developing an evaluation framework …
Optimizing Scm Proportions To Meet Multiple Performance Characters Of Ternary Concrete Mixtures Using Simplex-Centroid Design And Analysis Techniques, Sujay Math
All Dissertations
High performance concrete mixtures often contain multiple cementitious components. Among these, cement is the most expensive in addition to having a higher carbon footprint. Life cycle assessment of cement production reveals that the cement content is the most important factor in determining a concrete mixture's embodied energy and carbon footprint. Compressive strength, an important property of concrete, is directly related to the quantity of cement used in the mixture. However, higher quantities of cement lead to durability issues. The increased concerns about the durability of concrete over the past decade have increased focus on improving the long-term performance of concrete …
Freeze-Thaw Durability Of Portland Cement Concrete Due To Addition Of Crumb Rubber Aggregates, Shubhada Gadkar
Freeze-Thaw Durability Of Portland Cement Concrete Due To Addition Of Crumb Rubber Aggregates, Shubhada Gadkar
All Dissertations
Ground tire rubber also known as crumb rubber has been widely used in asphalt concrete over the past several years due to its ability to improve temperature susceptibility of asphalt binders and enhance the performance of asphalt pavements. However, its inclusion in portland cement concrete is comparatively recent and more research is needed before adopting it as a regular construction material. Past research has shown that while addition of rubber aggregates in concrete reduces its compressive, tensile and flexural strengths, but is useful in improving durability properties as freeze-thaw resistance due to the ability of crumb rubber to generate an …
Development And Evaluation Of An Intelligent Transportation Systems-Based Architecture For Electric Vehicles, Zhiyun Li
All Dissertations
The rapid development of increasingly complex in-vehicle electronics now offers an unprecedented level of convenience and versatility as well as accelerates the demand for connected driving experience, which can only be achieved in a comprehensive Intelligent Transportation Systems (ITS) technology based architecture. While a number of charging and range related issues continue to impede the Electric Vehicle (EV) market growth, integrating ITS technologies with EVs has the potential to address the problems and facilitate EV operations. This dissertation presents an ITS based vehicle infrastructure communication architecture in which abundant information can be exchanged in real time through vehicle-to-vehicle and vehicle-to- …